A. Field of the Invention
This invention relates to foaming and silt suspending compositions, and to a method of employing same, particularly in the context of treating subterranean formations.
B. Description of the Prior Art
Use of aqueous based stable foams in treating subterranean formations, such as in acidizing and/or fracturing to stimulate the production of oil and gas therefrom, or in well clean-up operations, has been known in the art for several years. Such foams generally contain a surfactant as an aid to generating and/or stabilizing the foam, i.e. a foaming agent.
It is also known to employ silt suspending agents in aqueous fluids for treating subterranean formations, particularly in acidizing fluids or in fluids for well cleanup immediately following an acidizing treatment, since failure to remove formation fines released during acidizing can result in decreased well productivity as a result of formation plugging and/or emulsification of the valuable formation fluids.
Silt suspending agents are generally cationic or amphoteric surfactants which provide silt suspending, water wetting, surface tension reducing, and to some extent, foaming, properties. Conventional silt suspending surfactants, however, do not perform well as foaming agents per se. On the other hand, the most efficient foaming agents of the prior art, which are generally anionic or nonionic surfactants, are not themselves sufficiently effective as silt suspending agents. Moreover, the nonionic and particularly the anionic foaming agents generally do not perform well in certain types of frequently employed aqueous based treating fluids, e.g. heavy brines, inhibited acids, and fluids containing cationic additives such as zirconium oxychloride, a frequently used clay stabilization agent.
Accordingly, a composition was sought which would be sufficiently stable to be stored, transported, and otherwise handled as a single item in inventory; which would impart both outstanding foaming and outstanding silt suspending properties to aqueous based fluids of the type suitable for use in treating subterranean formations; and which would be effective in a variety of such fluids, including fresh water, brine, acid, inhibited acid, and fluids containing other cationic additives.